1. Field of the Invention
The present invention relates to a method of automatically transferring an elastic yarn from a full-bobbin on a bobbin shaft to an empty-bobbin on another bobbin shaft in a winder which is continuously winding the elastic yarn, to improve the efficiency of an automatic transfer operation of the elastic yarn.
2. Description of the Related Art
An elastic yarn has specific characteristics i.e., a high stretchability, a high frictional property or the like, compared with a general-purpose synthetic fiber such as a polyamide fiber or a polyester fiber, and accordingly, the following specific yarn transfer methods have been applied for the transfer of an elastic yarn.
Japanese Unexamined Patent Publication (Kokai) No. 47-27634 disclosed a method of transferring a yarn wound continuously on a full-bobbin to an empty-bobbin wherein the full-bobbin driven by a friction roll is moved away from the friction roll, the empty-bobbin is placed in contact with the friction roll, to rotate the empty-bobbin and the full-bobbin stopped until the empty-bobbin is rotated at a desired rotational speed, so that the yarn is automatically wound on the empty-bobbin, i.e., the yarn slack between the empty-bobbin and the full-bobbin is wound on the full-bobbin and the slack yarn is stretched between the empty-bobbin and the full-bobbin and is broken.
Since, however the elastic yarn has a high stretchability, when the elastic yarn is broken by a stretching operation the elastic yarn slides on a circumferential surface of the bobbin during the recovery of an original length of the elastic yarn.
Accordingly, since the elastic yarn partially strikes the circumferential surface of the bobbin and a tension in portions of the elastic yarn striking the circumferential surface of the bobbin suddenly becomes zero, the elastic yarn is flexed, i.e., portions of the elastic yarn move away from the circumferential surface and other portions of the elastic yarn adhere to the circumferential surface.
Usually, the portions of the elastic yarn moved away from the circumferential surface are eventually adhered to the circumferential surface, and the elastic yarn then continuously wound on the empty-bobbin. Nevertheless, a high speed spinning method in which a rotational surface speed of the friction roll and the bobbin is remarkably increased has been introduced, and an elastic yarn having a finer denier than a conventional elastic yarn is used. In these cases, often the elastic yarn is not wound on the empty-bobbin but on the friction roller, and thus the automatic yarn transfer operation was not carried out.
It appears that the above failure of the automatic yarn transfer operation is caused by the separation of a portion of the elastic yarn from the empty-bobbin in contact with the friction roll, and a length per weight of the elastic yarn in contact with the friction roller becomes long when the high speed spinning system and/or the finer elastic yarn is used, and thus the elastic yarn is wound on the friction roll.
Further, since a running pathway of the elastic yarn released from a traverse device is not restricted in the method of Japanese Unexamined Patent (Kokai) No. 47-27634, the elastic yarn is always stretched in a direction parallel to an axis of the empty-bobbin on the circumferential surface of the empty-bobbin. Therefore, this condition may contribute to the failure of the automatic yarn transfer operation.
Japanese Examined Patent Publication (Kokoku) No. 1-22195 disclosed another method of automatically transferring an elastic yarn from a full-bobbins to an empty-bobbin. A winder implementing the transfer method disclosed in Japanese Examined Patent Publication (Kokoku) No. 1-22195 is schematically illustrated in FIG. 11(A) and FIG. 11(B). As shown in FIG. 11(A), this winder is composed of two bobbin shafts 5 and 6, a turret dish 4 rotatably supporting the bobbin shafts 5 and 6 at positions spaced apart by an angle of 180.degree. , a friction roll 1 able to come into contact with a bobbin 8 mounted on one of the two bobbin shafts 5 and 6 and driving the bobbin 8, and a traverse device 3. The winder is further provided with a yarn position restricting plate 7 arranged upstream of the traverse device 3 and having yarn guiding portions constituted by two inclined surfaces forming a yarn holding point at an end where the two inclined surfaces come together, and a yarn receiving opening formed between the other ends of the two inclined surfaces. When the elastic yarn is transferred from the full-bobbin to the empty-bobbin, the elastic yarn is released from the traverse device by turnings the yarn position restricting plate 7, and the positions of the full bobbin 8a and the empty-bobbin 8 are reversed by rotating the turret disk 4 through 180.degree. (see FIG. 11(A)) so that the empty-bobbin comes into contact with the friction roll 1, and thus the elastic yarn is held in a slit arranged in the circumferential direction of the bobbin 8 on a circumferential surface of the bobbin 8 and is cut.
Since the empty-bobbin comes into contact with the friction roll when the elastic yarn is transferred from the full-bobbin to the empty-bobbin, in the method disclosed in Japanese Examined Patent Publication (Kokoku) No. 1-22195, this method has a draw back in that the same failure of the yarn transfer process as of Japanese Unexamined patent publication (Kokai) No. 47-27634 is likely to occur.